/Engine/Source/Runtime/SlateCore/Public/Brushes/SlateBorderBrush.h
Similar toFSlateBoxBrushbut has no middle and the sides tile instead of stretching. The margin is applied exactly as inFSlateBoxBrush.
struct FSlateBorderBrush : public [FSlateBrush](API\Runtime\SlateCore\Styling\FSlateBrush)